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Thread: Sproggy Power Supply Question

  1. #1
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    Post Sproggy Power Supply Question

    Let me start by stating (as I have so many times before) that I'm not great with electronics, so this may very well be a dumb question but please humour me. I recently purchased a pre-made Sproggy power supply, and in looking over it and comparing it to the specs on Sproggy's site I have noticed a couple of things. For reference, here is a link to Sproggy's schematic: http://sproggy.mp3car.com/PSUMK25/psu2-5_placement.pdf
    First off, there is no ground wire comming into the supply. There is the +12 in and the remote wire, but no ground. Not a problem, I can add a ground wire easily. However, where should I connect this? Should it go to the car's negative ground off the battery or just to the car's metal frame?
    Next question: what do I do with the remote wire? Should I just ground this? I already have a switch on the +12V comming into the supply, so this is how I will turn it on and off.
    Final question: On the motherboard power connector (AT style), the orange wire is not going anywhere. Here is a link to Sproggy's connector diagram showing this wire: http://sproggy.mp3car.com/psumk25/psu2-5_wiring.pdf . On this diagram, the orange wirre is going to pin 1 on the motherboard connector, and from the looks of it the oriange wirte is supplying +5V just like the red wires. Is this wire required, or can I use the supply without it?

    I'm really excited about the prospect of ditching my inverter and using a DC-DC supply, so any help or advice would be greatly appreciated. Sorry for the long post!

    Mike.

  2. #2
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    Lets see if I can help a bit;

    Answer 1: Sorry the tell you, but on the schematic you referenced, there was a ground wire shown. The wire between the remote and the + wire is the ground wire. And yes you can connect this to the frame of you're car. The frame of your car is (or should be!) connected the the negative terminal of your battery under the hood somewhere.

    Answer 2: The remote wire requires a +12V bias to turn the power supply on. You can hook this up to a +12V switched signal (like off you're ignition). But if you have a swith already on you're +12V source you might as well tie the remote and the +12V lines you have together.

    Answer 3: As far as the Orange wire goes. It's a Power Good signal. If you're current motherboard doesn't use it then you should be able to run just fine without it.

    Hope this helps...

    [ 09-22-2001: Message edited by: littlej ]
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  3. #3
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    Thanks LittleJ! I just tested the supply (not in the car, used a spare computer PSU to provide the +12V) and it works. I powered my SBC (Advantech PCM-5862 which is to become my new car player), the CPU fan and a hard drive from the Sproggy supply and it ran, but seemed to get pretty hot.
    You mentionned in another post that your Sproggy supply was not giving you enough power for 12V. I'm wondering if I should be OK with this setup:
    - SBC (only needs +5V, 7A) with P-133 CPU
    - WD 6.4GB hard drive (specs on the drive claim 250mA idle and 500mA seek for 12V, 480mA for 5V)
    - 1 CPU fan + 1 case fan (each need 80mA)
    - 4" LCD (requires 12v at 500mA)
    If I add all this up, it looks like I'm running 1.16A for the +12V and 7.48A for the +5V when the hard drive is seeking. When the hard driuve is idle, it needs 910mA for +12V and 7.48A for +5V. According to Sproggy's site, the supply is good for 1.3A for +12V and 10A for +5V. Am I cutting it too close?
    My options are to run the CPU fan and the case fan directly off the +12V from the car and/or to run the LCD from the car. This would free up 660mA, meaning that I'd only be pulling 500mA from the +12V on the Sproggy.
    Sorry for yet another long post, I just want to get this right!

    Thanks,
    Mike.

  4. #4
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    Hey no prob whatever I can do to help.

    Yeah I did mention in another post that I was having problems with the +12V current on my PSU. From your current calculations it looks like your +5V will be okay (same as mine was) and your +12V should be okay. That's what I thought with mine too but it was hit and miss with turning on the motherboard with the drives I had (HD and DVD). The thing I didn't take into account was the "turn-on" current requirements to get the motors in the HD and DVD spinning is more than the "running" current requirements printed on the devices. So what I would do is like you suggested; run as much "non-logic" stuff as possible off the +12V from your car. Stuff like fans, LCD backlights, etc. Anything that will run on voltages between +11V and +14V (which is a range I've seen in my car), and doesn't need a regulated +12V signal.

    I noticed the same thing you did too with heat. I noticed that the MAX787 on my PSU got pretty hot, so what I did was "mutate" the PSU design a bit and added a second MAX787 which seemed to help alot with my heat problem. Check out my little web page from my signature below and it should show you what I did... Hopefully Sproggy doesn't get too mad at me.

    Hope this helps a bit.

    [ 09-23-2001: Message edited by: littlej ]
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    Originally posted by littlej:
    <STRONG>Anything that will run on voltages between +11V and +14V (which is a range I've seen in my car), and doesn't need a regulated +12V signal.
    </STRONG>
    I don't see why you can't run the HD 12v directly from the battery! In fact,in my first project I also used Sproggy's PSU,and also I didn't have enough current for HD (it wasn't spinning up),so I used 12v directly from the battery.At first I was afraid about the voltage vould rise to 13-14v when the engine was running,but this setup worked for me for a year,without problems with HD.
    Enjoint life!

  6. #6
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    I'm glad to hear that worked for you. Trust me I've been tempted to do the same thing. But I just suggested not running the HD off of the alternator directly because not only is the the power dirty (lots of high frequency noise induced on it) but it could vary pretty wildly. Thats why I suggested at least running some 7812's and filtering the output using a capacitor or a few capacitors.

    Its good to hear that even without regulated power the HD will survive. Thanks man.
    j
    j's MP3Car.com Web Site
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  7. #7
    Retired Admin Aaron Cake's Avatar
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    Cool

    Running the HD off the car's 12V is a really bad idea. That voltage may swing from about 8V to 16V or slightly more. Way out of the operating specs of a standard HD. Also, that power source is very dirty, containing surges, spikes, sags, noise, etc.
    Player: Pentium 166MMX, Amptron 598LMR MB w/onboard Sound, Video, LAN, 10.2 Gig Fujitsu Laptop HD, Arise 865 DC-DC Converter, Lexan Case, Custom Software w/Voice Interface, MS Access Based Playlists
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  8. #8
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    Actually,it's not containing any spikes,because car's battery is acting like big capacitor,and therefore filtering any spikes.And I don't understand what are you talking about high frequencies? Connect a scope to the battery,turn the car on and see the voltage.Very clean,no spikes when igniting,just voltage rises to 13-14v when you push gas pedal.
    And 2-3v more won't kill the HD - my first project is the evidence!If you wanna know,it was Western Digital 8 GB model.
    Enjoint life!

  9. #9
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    I know why this guy sees no problems with running the hd straight from the battery, check out his interests, he probably couldn't even see the scope, he was probably tripping...

  10. #10
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    Skinny,you have crossed your 450 post...slow down.
    By the way,I'm not sure at all that you know what scope is it.

    [ 09-29-2001: Message edited by: Dima ]
    Enjoint life!

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